Hydrocarbon conversion



April; 24,1945.

.L A. ANDERsN nYDRocARBon'oNvERsIQN Filed July 51,' .1942

atented pr. 24, 1945 2,374,262 aocaaeou coN-vuusxou rum A. anderson, chicago, ni., .assigner to Sd @ll-Company, Chicago, ill., a coration oi Indiana Application `iully 3l, i942, Serial No. 452,951

9 illaims.

and produce products of high octane number.

'Furthermore the presence of even this small tion fuels and is concerned more particularly with the conversion of oleiinic hydrocarbons and isoparallnic hydrocarbons to isoparafiinic hydrocarbons of higher molecular weight.

It has been shownthata mixture ofoleflnic hydrocarbons and isoparamnic hydrocarbons will combine to iorm isoparanic hydrocarbons of higher molecular weight and of excellent octane number but the exact chemical reaction is not too well understood, although it is generally believed that there is a joining oi the olelnic andl isoparanic hydrocarbons, possibly through the formation of some olenic intermediary or un usual activation of the isopara'n. The exact reaction involved is immaterial from the point of view of my invention, it only being necessary tional operating temperatures.

.ments andembodiments of this invention will become apparent as the description thereof pro-AC to know that a mixture o olenic and isoparaiionic hydrocarbons contacted in the presence of a catalyst will produce a high octane number :fuel ci proper boiling range and of higher molecular weight. The reaction is generally referred to as'alliylation although .other terms such as 'dehydroalliylatiori9 condensation, etc., have been applied. For the salreoi simplicity I vvill'here-v inafter refer, to 'the process as one involving allsylation and the product as an alkylatef 'it is en object of this invention to provide an improved sulfuric acid alkylation process for increasing the yield of product per unit of sulfuric acid fed to the process. Alinotl'ier obiect of this invention is to provide an improved process for the production of alkylate using as a catalyst .sulfuric acid oi extremely high acidity. A still further object-oi this invention is to provide a process for the use of sulfuric acid in an alkyla tion process at concentrations substantially lower than have heretofore been employed. More particularly it is an object otthis invention to provide an improved sulfuric acid alkylation process wherein'the composition of the catalyst is maintained within certain denite limits. l Further objects and advantages of this invention will become ,apparent as the description thereof pro-J c'eeds.

A I have discovered -that when sulfur dioxide is present'ln a sulfuric acid alkylation system utilizing the conventional -92 to 98% sulfuric acid, 'the yield of alkylate .per unitof olen charged isvery severely reduced.. IEven atfairly .low temperatures, determinable amounts oi S02; are formed during lthe reaction, and-as the temperature employed increases, the S0; formed also increases but' to a greater extent. 0n the other hand, I

e have discovered that vif but definite amounts of sulfur dioxide'are present, acids having from about 98 to about 106% acidity, for example 104% sulfuric acid, will, promote excellentalkylatlon amount of sulfur dioxide will depress the freezing point of 'the strong acids to an extent permitting their use in an alwlation process at conven- Various refineceeds. v

'The accompanying drawing forms-a part of the specication and is a simplied diagram of apparatus suitable for carrying outpne embodiment of my process.

In brief this invention contemplates passing a feed stock comprising oleflns and isoparamns through an alkylation zone in the presence of sulfuric acid having a titratable acidity in the approximate vicinity of to 98% and in the substantial absence of sulfur dioxide and also through a reaction acne in contact with a sulfuric-acid having a titratable acidity in the approximate vicinity of 98 to 106% and inthe presence of from aboutill to 5.0% of sulfur dioxide. The acid exhausted from the high acidity zone is thereafter used in the low-acidity zone. i

As isoparamnic hydrocarbons suitable for my process i can employ low boiling hydrocarbons 4such as isobutane, isopentane, isohexane or mixtures of any tivo or more of these hydrocarbons either with or without the corresponding normal parafns. For practical reasons l prefer to em- '.ploy isobutane as the isoparafnic hydrocarbon 'since vthe Cs and' Ce hydrocarbons und excellent use as blending stocks for aviation gasoline to 'supply the necessary volatility characteristics as not by any means excluded from contemplated use. A

The oleins can comprise any normally gaseous mono-olefin such as propylene or the butylenes (including both the normal butenes and isobutylene) and may include the amylenes or higher boiling olenns. The dimers, copolymers, cross polymers,` etc., of these olens can also be used since under alkylation conditions they appear to give products similar to those obtained with the low boiling oleins. Ordinarily ethylene is not a suitable olefin since it reacts only with diilculty if at all with an isopar in the presence of sulfuric acid. For the sake oi simplicity the process will be described with reference to the use of isobutane and oleflns having tour carbon atoms per molcule which may or may not be mixtures of normal lbutenes and lsobutylene. The

term butylenes" as employedin the description of my process is intended to include either the Vnormal butenes or isobutylene or mixtures in any proportions and is not to be considered as referring to normal butenes only.

Referring now to the drawing, a feed stock comprising a mixture of isobutane and butylenes from source Ill is pumped through line Il by pump I2 to an alkylation reactor A. 'Ihe isobutane and butylene mixture can suitably be obtained `from a refinery butane cut from the debutanizaticn of cracked gasolines or prepared by the partial dehydrogenation of a virgin or natural gas butane stream. Another suitable source'includes the off-gases from selective polymerization of a refinery butane cut from which substantially all of the isobutylene has been removed by conversion to the dimer without appreciable co-polymerization of normal butenes and isobutylene.v The feed passes through a mixing header and nozzles IE into alkylation reactor A where it is contacted with sulfuric acid and passes upwardly therethrough. The reactors can be any l conventional means for contacting the hydrocarbons and catalyst; but desirably are, as illustrated, of a tower typecontaining a deep pool of sulfuric acid. The upper portion of reactor LA is enlarged to permit separation of hydrocarbons from the emulsion or `suspension, a portion of this emulsion being withdrawn from the interface through line I3 and pump I4 and returned to mixing header and nozzles I5. Sulfuric acid from a source to be described later is introduced byline I6 to mixing header IE. Additional isobutane from source to be described later is introduced through line I1 to line II and header I E. The

isobutane from source IG and line I I is such that the external isobutane to oleiln ratio is of the order of about 2 to about 7 or more, for example about 4; that is, the quantity of isobutane from line I plus that in the feed from source I divided by the quantity of oleflns in the feed will be of the order specified above. By recycling hydrocarbons fr: the upper part of the reaction zone A through .me I8 to header I5 the internal isobutane-to-olenv ratio will be very -much greater and of the order of 100- or more. The quantity of hydrocarbons passing through pump I4 compared with theentering pump I2 can be of the ratio of about to about 10 or more.

Hydrocarbons are withdrawn from the top of reactor A through line 'I8 and can be introduced into reactor B through header and nozzles I9 where they pass upwardly in contact with catalyst. to be described in more detail later.- Reactor B 'perature conditions prevailing in reactorB and at the same time reduces the tendency of the strong acid to b urn" the hydrocarbon material. AThe SO2 is added in suchamountsthat the eventual concentration of SO2 in reactor B will be within the approximate range of about 0.1 to

about 5.0%, preferably about 2%,and the titratable acidity of the acid in reactor B will be of the order of about 98 to 106%, preferably about 102 to 104%. Alkylate formed or treated in the presence of such high strength acid possesses exceptionally high octane number.

Acid is continuously withdrawn from reactor B through line 30 to stripper 3i wherein the SO2 is removed and passed through acid plant S for vconversion to SOsor recycled via line 28 as makeup SO2. SO2 free acid is withdraw'nfrom stripper 3| by pump 32 and line I'S and introduced into reactor A, by the means' previously described. If, as described, the flow of reactants is through reactor A and reactor B in series, reactor A can be operated undersuch conditions and to such en through une sa to stripper 34 the sot formed during the reaction in reactor A can be removed and the acid returned via line 35 and pump 36 v to line I6 and reactor A. Spent acid can be withdrawn from-stripper 34 through line 31. The

- or a. stripping medium can be introduced into I strippers can advantageously -be vacuum strippers strippers 3l and 34 by lines 38 and 39 respectively. Nitrogen, carbon dioxide, etc., can be used as stripping mediums but preferably air is employed. Hydrocarbon gases, such aspropane or butano, can be used, and theSOz subecuuently recovered. If air is used it can ,be withdrawn through line 40 and directed to acid plant S tol gether with the SO2 removed thereby and introduced into a sulfur burnerand the SO2 -thus recovered. 1

Since sulfur dioxide has 9, high solubility in hydrocarbons a substantial portion of the SO2 in- -troduced via lines 28 and- 29 toreactor B will be hydrocarbonsl from the enlarged section of' 'reactor B are withdrawn through line 20 and directed to subsequent separation equipment. If desired or' necessary, additional oletlns can be introduced into reactor B through line 2l via line I8 and additional isobutane can also be introduced into reactor B through line 22. In reactor B asin reactor A, mixed hydrocarbons and acid can be withdrawn from the interface in the enlarged settling zone and recycled to header I 9 through line 23 and pump 24.

Sulfuric acid for carrying out my process can be derived from an acid plant S charging 'sulfur and oxygen from sources 25 and 26, respectively. Either fuming sulfuric acid having a titratable acidity of from about 100% to about 106%, or SO: from line 21 is admixed with SO2 from line 28, the combined streams being directed via line 28 to alkylation reactor B. The sulfur dioxide serves the double purpose of depressing the freez'- ing point of the fuming acid or sulfur trloxide so that it will operate satisfactorily under low temcarried overhead therefrom through line 20. A

portion of the acid from the base of stripper 3| is passed through line 4I to scrubber 42' to re cover SO2 fromthe hydrocarbons and the rich acid withdrawn from scrubber 42 through line I3 any unreacted hydrocarbons including normal parafns originally present, pass overhead from scrubber d2 through line 44 to scrubber 45 which can be either a caustic scrubber, a'water scrub-- ber or a combination thereof ,wherein the last traces of acid and sulfur dioxide lare removed from the hydrocarbons. Spent water and/or caustic is withdrawn from scrubber 45 through line 46 and the washed hydrocarbons are directed through line 4l to a fractionation system.

The fractionation system can be arranged in a variety of ways conventional in the art. The manner illustrated involves debutanization followed by fractionation to recover isobutane.' In

the fractionating system as shownithe hydrocarbons pass throughheat exchanger 48 to de- 'butanizeri 49 wherein a separation is'made between C-i and heavier hydrocarbons, the ltotal alkylate being with drawn through line 5U to rerun equipment (not shown) wherein hydrocarbons of aviation gasoline boiling range can be recovered from any higher boiling elkylcte which may here been formed by "over-alkylotionf in the reactors. The overhead butano and lighter fraction from debutenizer te is cooled in condenser i, collected in drum 52 and e portion returned es redux to debutanizcr it by line to und pump 5t. The gases lighter than butano 'for conversion to isobutene in isomerizetion equipment (not shown) for use in the elkylation system herein described. The butenes from the v isomerizetion step cen be returned to superfrsc tionotor 5t for the recovery or isobutanethere froin. The isobutsne posses overhead through line 5t?, is cooled in condenser @il collected in drum o iv sind s portion returned es reur. through lines sind pump The remaining isobutenc is recycled to the process vie. lines t@ and lines il and 2s as previously described.

Seversl. types of omretion are contemplated within the scope of this application; for .mi ple, eliryletlori cen be effected in reactor A with conventional scid end the reaction' products therefrom passed through reactor E for finishing" in the presence of strong acid. As e, varietion thereof, ellryletion conditions can oe mein toineclzi reactor fi end additional olens und iso butano fed to reactor' together with the reactents from reector A for the'procluct'lon oi "improved elkylcte. Another method oi operation preferably in the 'presence of additional amounts of isooutone.

The press can oleo be ceri-led out by emplaying persllel operation of reactors A and B. In this event feed stools from source i@ is sent to both reactors A end B through lines ii and 2i, respectively. Additional isobutene is introduced into both reectors through lines4 il und 22, rcsrectiveiy. The usuel `emulsion recycle in the are operated either at e very low vacuum to insure substantially complete removal of SO2 therefrom or an inert stripping ses such as nitrogen,

carbon dioxide or dry air can be introduced, or

both. .In the event that the acid plant is located in the vicinity of the alkylation plenfl and con vement thereto air is probably preferable since itcan be introduced with the stripped gases into the sulfur burners of the acid plant for recovery and conversion of the sulfur products.

An importent feature of this process is the usel l of acid at two dierent strengths. In reector B it is used at e very high acidity level within the range described and SO2 is introduced with the high acidity acid to avoid sclidificationthereof'and to conti-oline tendency of the acid to decompose or cher the hydrocarbons present. acid is withdrawn from reactor B, the Sr removed therefrom and the Srwree acid used et the acid strength previously described in reector A for the alkylation or` hydrocarbon feed stock therein. The acid will be discharged from theentire system in smaller quantities and usually at lower icid strength than would be the cese if a. single reactor were used. 'lhe"dilution" ofthe strong acid in reactor B serves to condition the acid for use in reactor A, while simultaneouy converting additional quantities of hydrocarbons to high octane number eviction fuelsor improving the knock rating of the olkylete from reactor A, or both. The introduction of 80s into reactor B has the added adventege'of permitting operation at a higher temperature than would otherwise be possible. Grdinarily, fumingecid is so strong it hes a'great tendency to char or oxidize the hydrocarbons present, particularly if elevated temperatures aroused. The SO2 ap Yperenty has e. dampening eect on the furning acid without interfering withits ability to promote alkylation Moreover, provision is made in this process for the removal of S02 from the alryletion scid in reactor A both prior to the introduction of scid from reactor B and before recycle of the scid in the reactor itself. 'This removal ci SO2 increeses the activity of the cate.-

lyst enel prolonge catalyst life as well as increasing the yield of cllsyiete obtained. per unit of The' reactors sind withdrawal of hydrocarbons is as Run A .mm3 Elmo indicated except that the product from reactor lsobutanetoisobu leneratlo.. 3.6.. 3.2 3.1. actor A inthe manner previously described. Acidmoieanwaig mio i.z... 1.1-' 1.

The following conditions are recommended for Yfdwalkylatefpef mi 71 69: 130- o the operation of reactors A and B..

Range VEixample Range 'Exemple i Temperature F.- 50 5D Pressure p.s.i.sbs lil-200 35 1 1 lo External isobutane to olei-ln ratio. 2/1 to 8/1 2/1 2/1 to 8/1 3/1 Internal lsobutsne to olelin ratio 3/1 to 100 l 50/1 3/1 to 1D0/l .5o/1 S0; conoentratloninecid percent Lessthan .l Lessthan0.l 0.1'to6 2 Depth ci scid bed leet.; lil-40 15 10-40 l5 It is preferable that strippers 3i and 34 be op eretcd et or neer the temperatures of the alkyla.- tion reaction and desirably the temperaturev Runs A and B were carried out in a batch reactor with `the slow controlledaddition of isobutylene so that instantaneous isobutene in oleslould not exceed about 75 F. .The strippers fw iin ratio was extremely high.- The seine condi.

tions were-used in each experiment and` it is to be noted thatthe alkylation conditions were excellent, as witnessed bythe high yield obtained in run A. Inrun B the addition of a small amount namely 3%, of SO2 to the reaction ,zone dropped the yield from 171% based on the oleilns t0 only 69%.

Run C illustrates the use of fuming sulfuric acid with the addition of 3% SO2 thereto. It will be 4noted that the yield, while not as great as that and in locations where seasonal temperatures are excessive and cooling waters not readily available this becomes cf considerable importance. By continuously withdrawing a portion of the alkylation Aacid from reactor A andremoving the SO2 therefrom before recycling, increased tempera4 number fuels which comprises contacting isoparailiniccand oleinic hydrocarbons in a rst reactor under alkylation conditions, in the presence unreacted hydrocarbons to a second reactor for contact under alkylation conditions with sulfuric acid having a titratable acidity withinl the approximate range of 98% to 106% and containing .SO2 in an amount within the approximate range of 0.1% to 5.0%, separating hydrocarbon products and unreacted hydrocarbons from the sulfuric tures can be employed without sacrice of alkylate yield. i

Probably the most outstanding advantage for my process over sulfuric acid alkylation processes previously known and described in the art is the increased yield ci alkylate per unit of acid. If, for example, the acid in reactor A is allowed to deteriorate to about 8086% acidity (much lower than hasheretofore been thought commercially desirable) the polymers formed as a result are not detrimental to the aviation fuel value of product but are converted in the strong acid system to desired alkylate. If the feed streamsare directed to the reactors in parallel, then the alkylates from the strong acid alkylation and from the conventional acid alkylation are cumulative, with only a single acid stream fed to the system.

Although I have illustrated apparatus suitable for carrying out one embodiment of my inven-4 tion, Ldo notintend to be limited thereto but Aonly in so far as is set forth in the appended claims. Various details have been omitted from the drawing for the sake of simplicity and clarity, such details including sulfuric acid production equipment, heat exchangers, valves, pumps, automatic controls, etc., the necessity for which will be recognized by one skilled in the art wishing to practice my invention.

I claim:

1. Aprocess for the production of high octane number'fuels which comprises contacting isoparamnic and oleiinic hydrocarbons in a iirst reactor in the presence of sulfuric acid having a titratable acidity within the approximate range of 80 to 98% under alkylation conditions, maintaining said sulfuric acid substantially SO2-free, contacting isoparaillnic and olenic hydrocarbons in a second reactor in the presence of sulfuric acid having a titratable acidity within the approximaterange of 98% to 106% and containing SO2 acid and SO2 from said second reactor, removing SO: from at least a portion of said separated acid from said second reactor, directing the SO2-free acid therefrom to said rst reactor, and recovering hydrocarbons of gasoline boiling range from said separated hydrocarbon products from said second reactor.

3. A process for the production of high octane number fuelswhich comprises contacting an isoparaiiin with an olefin in the presence of sulfuric acid having a titratable acidity within the ap; proximate range of 80 to 98% under alkylation conditions, maintaining the SO2 content of said acid at below about 0.1% by continuously withdrawing at least a portion of the acid separately from said contacting step, recovering SO2 by f stripping from said withdrawn acid, and supplying the stripped acid having a titratable acidity within said range to the said contacting step.

taining between about 0.1% and about 5.0% S025 withdrawing acid from said contacting step, recovering SOz from the withdrawn acid, and adding at least a portion of the recovered SO2 to the sulfuric acid supplied to the contacting step,

5. A process for the production of high octane number fuels which comprises contacting isoparailinic and oleiinic hydrocarbons at an alkYlation temperature in the presence of sulfuric acid having a titratable acidity within the approximate range of about 98% to 106%. maintaining between about 0.1% and about 5.0% SO2 in the contacting step, continuously withdrawing gasecus reaction eilluent including SO2 overhead from said contacting step, separately withdrawing a portion of the sulfuric acid from said contacting step, subjecting the withdrawn acid to a stripping operation, scrubbing the SO2 from said reaction eiiluent with at least ay portion of the stripped acid, recovering an SO2-rich acid from the scrubber, and supplying to the ntacting step at least a portion of the said SO2-rich acid having a net SO2 content of between about 0.1 and 5%.

A6. In a sulfuric acid alkylation process, the

steps comprising contacting underl alkylation' proximate range of 98% to 106% and containing S0: in an amount within the approximate range l.of 0.1 to 5.0%, separating alkylate and unreacted hydrocarbons from said sulfuric acid and recycling at least a portionof said separated sul-' furic acid and S02 to said contacting step, withdrawing at least a portion ofgrsaid separated sulfuric acid and SO2, removing SO: from said withl drawn acid, contacting under alkylation conditions an acid having a titratablefacidity within the approximate range of 80 to 98% with hydrocarbon mixtures containing isoparaiiinic and oleiinic hydrocarbons, directing said SO2-free Withdrawn acid to said last-mentioned contacting step, separating hydrocarbon products and un.- reacd hydrocarbons fromhsulfuric acidin said last-mentioned contactingstep, recycling at least a portion of said separated acid to said last-mentioned contacting step and continuously withdrawing at least a portion of said last-mentioned 'separated acid.

'1. In the sulfuric acid alkylation process of claim 6, the further step of removing SO2 from' said portion of separated acidi'rom said lastthan that maintained during the contacting utep, reducing the vSO2 content of the withdrawn acid to less than ,0.1% by stripping'. supplying the stripped acid to a second paramnic and oleflnic hydrocarbon contacting step, maintaining the SO2 content in the second contacting step at less v than about 0.1%, and supplying at least a part mentioned contacting step before recycling said f acid to said contacting step. n

8. In the process for the production of high octane number fuels which includes the step of contacting olefinic and lparailinic hydrocarbons at an alkylation temperature in the presence of sulfuric acid, the improvement which comprises employing sulfuric acid having a titratable acidity within the approximate range of about 98% to 106%, maintaining between about 0.1% and about 5.0% of SO2` in said contacting step, continuously withdrawing from said contacting step- -a sulfuric acid having' a titratable acidity lower of about 98% to 106%, maintaining between about 0.1% and about 5.0% SO2 in said contactingv step, continuously withdrawing from said contacting step sulfuric acid having a titratable acidity below that maintained in the rst Acontacting step, reducing the SO2 content of the Vwithdrawn acid by stripping, supplying the stripped acid to a second contacting step, cont'acting ispparaflinic and oleiinic hydrocarbons with said `acid in said second .contacting step at an alkylation temperaturefmaintaining sulfuric acid within said second contacting step at a titratable acidity of between about and about 98%, withdrawing acid from said contactlng step, stripping SO: from acid withdrawn from the second contacting step, and supplyingto the rst contacting step at least a part of the SO2 recovered by the strippings. g

JOHN A. ANDERSON. 

